Commit 9126d275 authored by Andrew Price's avatar Andrew Price Committed by Andreas Gruenbacher
Browse files

gfs2: Don't clear sb->s_fs_info in gfs2_sys_fs_add 



When gfs2_sys_fs_add() fails, it sets sb->s_fs_info to NULL on its error
path (see commit 0d515210 ("GFS2: Add kobject release method")).
The intention seems to be to prevent dereferencing sb->s_fs_info once
the object pointed to has been deallocated, but that would be better
achieved by setting the pointer to NULL in free_sbd().

As a consequence, when the call to gfs2_sys_fs_add() fails in
gfs2_fill_super(), sdp = GFS2_SB(inode) will evaluate to NULL in iput()
-> gfs2_drop_inode(), and accessing sdp->sd_flags will be a NULL pointer
dereference.

Fix that by only setting sb->s_fs_info to NULL when actually freeing the
object pointed to in free_sbd().

Fixes: ae9f3bd8 ("gfs2: replace sd_aspace with sd_inode")
Reported-by: default avatar <syzbot+b12826218502df019f9d@syzkaller.appspotmail.com>
Signed-off-by: default avatarAndrew Price <anprice@redhat.com>
Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
parent 914873bc

fs/gfs2/ops_fstype.c

+3 −1
Original line number Diff line number Diff line
@@ -64,7 +64,10 @@ static void gfs2_tune_init(struct gfs2_tune *gt) 


void free_sbd(struct gfs2_sbd *sdp)

{

	struct super_block *sb = sdp->sd_vfs;



	free_percpu(sdp->sd_lkstats);

	sb->s_fs_info = NULL;

	kfree(sdp);

}
@@ -1314,7 +1317,6 @@ static int gfs2_fill_super(struct super_block *sb, struct fs_context *fc) 
	iput(sdp->sd_inode);

fail_free:

	free_sbd(sdp);

	sb->s_fs_info = NULL;

	return error;

}

fs/gfs2/sys.c

+0 −1
Original line number Diff line number Diff line
@@ -764,7 +764,6 @@ int gfs2_sys_fs_add(struct gfs2_sbd *sdp) 
	fs_err(sdp, "error %d adding sysfs files\n", error);

	kobject_put(&sdp->sd_kobj);

	wait_for_completion(&sdp->sd_kobj_unregister);

	sb->s_fs_info = NULL;

	return error;

}